shpawn - Spawn a UNIX process using a shell and redirect stdin and stdout.
CommandString shpawn } { Flag=0: Status NormalExitFlag
CommandArray shpawn } {
} { Flag=1 or omitted:
CommandString Flag shpawn } -> { ear(write) mouth(read)
CommandArray Flag shpawn } {
{ Flag=2: ChildPID ear(write) mouth(read)
%try these examples with "spawn" as well to see the difference:
1. (echo $PATH) 0 shpawn
2. (rm synod2/lib/help/cc/*.hlp) 0 shpawn
3. (ls | sort) 0 shpawn
"shpawn" does the same as "spawn" does (see there).
However, the command is not executed directly but is passed
to a shell which then will process the command.
This way it is possible to use the full functionality of a
shell, e.g. wildcard extension, alias, piping, ...
By default, /bin/sh is used as the shell binary, and a login
shell is requested by giving the -l flag. These values can be
changed in the options dictionary, see sections "Options" below.
In addition, the piping facility of the shell can be used to
monitor the standard input and standard output of the
invoked command. Monitoring can conveniently be turned on
for stdin and stdout independently, via the options
dictionary.
See sections "Options" and "Remarks" below.
-see "spawn"-
Options-name: /shpawn
Option type default description
---------------- ---------- -------- ------------------------------
/terminal string $TERM Terminal command to be used for
monitoring stdin and stdout.
/monitor-stdin booltype false True, if the standard input of
the invoked command shall be
monitored in a terminal window.
/monitor-stout booltype false True, if the standard output of
the invoked command shall be
monitored in a terminal window.
/sh-binary string (/bin/sh) Path to the shell binary to use.
This binary must accept the flag -c
for execution of a command.
/sh-flags stringarray [] Flags added wehn calling the shell
binary. Flags must be given as separate
string elements (e.g. [(-l)].
The array may be empty.
The flag -c is automatically added
to this list of flags by the routine.
-see "spawn"-
-see "spawn"-
"shpawn" invokes "/sh-binary" from the options dictionary
(/bin/sh by default) and passes the given command after
a "-c" flag. This means the specified shell binary must
support this -c flag.
The monitoring option for stdin and stdout exploits the
piping deature of the shell, by piping information through
instances of the "tee" command, which writes it to a file.
(tee infile | command | tee outfile).
These files are then monitored in separate subprocesses, using
"tail" in a terminal window. The terminal command to be used is
defined in the Options of shpawn.
See manpages of sh, tee, tail, xterm/konsole for references.
The monitoring option creates two files named
/tmp/SLI-shpawn-monitor-stdin and /tmp/SLI-shpawn-monitor-stdout,
which will persist after command execution terminated, so
that their contents may be analyzed.
R Kupper
May 19 1999
/var/www/debian/nest/nest-simulator-2.20.0/lib/sli/processes.sli